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<FONT color="green">001</FONT>    <a name="line.1"></a>
<FONT color="green">002</FONT>    /*<a name="line.2"></a>
<FONT color="green">003</FONT>     * Copyright (C) 2011 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<FONT color="green">004</FONT>     *<a name="line.4"></a>
<FONT color="green">005</FONT>     * $Id: ByteArrayEncoder.html 4 2011-02-05 22:22:47Z archie.cobbs $<a name="line.5"></a>
<FONT color="green">006</FONT>     */<a name="line.6"></a>
<FONT color="green">007</FONT>    <a name="line.7"></a>
<FONT color="green">008</FONT>    package org.dellroad.stuff.string;<a name="line.8"></a>
<FONT color="green">009</FONT>    <a name="line.9"></a>
<FONT color="green">010</FONT>    /**<a name="line.10"></a>
<FONT color="green">011</FONT>     * Encodes {@code byte[]} arrays to and from hexadecimal strings.<a name="line.11"></a>
<FONT color="green">012</FONT>     */<a name="line.12"></a>
<FONT color="green">013</FONT>    public final class ByteArrayEncoder {<a name="line.13"></a>
<FONT color="green">014</FONT>    <a name="line.14"></a>
<FONT color="green">015</FONT>        private ByteArrayEncoder() {<a name="line.15"></a>
<FONT color="green">016</FONT>        }<a name="line.16"></a>
<FONT color="green">017</FONT>    <a name="line.17"></a>
<FONT color="green">018</FONT>        /**<a name="line.18"></a>
<FONT color="green">019</FONT>         * Encode a {@code byte[]} array as a {@link String}.<a name="line.19"></a>
<FONT color="green">020</FONT>         * Equivalent to:<a name="line.20"></a>
<FONT color="green">021</FONT>         * &lt;blockquote&gt;<a name="line.21"></a>
<FONT color="green">022</FONT>         * &lt;code&gt;encode(array, 0, array.length)&lt;/code&gt;<a name="line.22"></a>
<FONT color="green">023</FONT>         * &lt;/blockquote&gt;<a name="line.23"></a>
<FONT color="green">024</FONT>         *<a name="line.24"></a>
<FONT color="green">025</FONT>         * @param array byte array, or {@code null}<a name="line.25"></a>
<FONT color="green">026</FONT>         * @return hexadecimal string (or {@code null} if {@code array} was {@code null})<a name="line.26"></a>
<FONT color="green">027</FONT>         */<a name="line.27"></a>
<FONT color="green">028</FONT>        public static String encode(byte[] array) {<a name="line.28"></a>
<FONT color="green">029</FONT>            return encode(array, 0, array.length);<a name="line.29"></a>
<FONT color="green">030</FONT>        }<a name="line.30"></a>
<FONT color="green">031</FONT>    <a name="line.31"></a>
<FONT color="green">032</FONT>        /**<a name="line.32"></a>
<FONT color="green">033</FONT>         * Encode a {@code byte[]} array as a {@link String}.<a name="line.33"></a>
<FONT color="green">034</FONT>         *<a name="line.34"></a>
<FONT color="green">035</FONT>         * @param array byte array, or {@code null}<a name="line.35"></a>
<FONT color="green">036</FONT>         * @param off   offset into the array<a name="line.36"></a>
<FONT color="green">037</FONT>         * @param len   number of bytes to convert<a name="line.37"></a>
<FONT color="green">038</FONT>         * @return hexadecimal string (or {@code null} if {@code array} was {@code null})<a name="line.38"></a>
<FONT color="green">039</FONT>         * @throws IndexOutOfBoundsException if array bounds are exceeded<a name="line.39"></a>
<FONT color="green">040</FONT>         * @throws IllegalArgumentException  if {@code len} is greater than {@code Integer.MAX_VALUE / 2}<a name="line.40"></a>
<FONT color="green">041</FONT>         */<a name="line.41"></a>
<FONT color="green">042</FONT>        public static String encode(byte[] array, int off, int len) {<a name="line.42"></a>
<FONT color="green">043</FONT>    <a name="line.43"></a>
<FONT color="green">044</FONT>            // Check for null<a name="line.44"></a>
<FONT color="green">045</FONT>            if (array == null)<a name="line.45"></a>
<FONT color="green">046</FONT>                return null;<a name="line.46"></a>
<FONT color="green">047</FONT>    <a name="line.47"></a>
<FONT color="green">048</FONT>            // Check bounds<a name="line.48"></a>
<FONT color="green">049</FONT>            if (off &lt; 0 || len &lt; 0 || off + len &lt; 0 || off + len &gt; array.length)<a name="line.49"></a>
<FONT color="green">050</FONT>                throw new IndexOutOfBoundsException("array bounds exceeded");<a name="line.50"></a>
<FONT color="green">051</FONT>    <a name="line.51"></a>
<FONT color="green">052</FONT>            // Encode bytes<a name="line.52"></a>
<FONT color="green">053</FONT>            if (len &gt; Integer.MAX_VALUE / 2)<a name="line.53"></a>
<FONT color="green">054</FONT>                throw new IllegalArgumentException("array is too long");<a name="line.54"></a>
<FONT color="green">055</FONT>            char[] buf = new char[len * 2];<a name="line.55"></a>
<FONT color="green">056</FONT>            for (int i = 0; i &lt; len; i++) {<a name="line.56"></a>
<FONT color="green">057</FONT>                int value = array[off + i] &amp; 0xff;<a name="line.57"></a>
<FONT color="green">058</FONT>                buf[i * 2] = Character.forDigit(value &gt;&gt; 4, 16);<a name="line.58"></a>
<FONT color="green">059</FONT>                buf[i * 2 + 1] = Character.forDigit(value &amp; 0xf, 16);<a name="line.59"></a>
<FONT color="green">060</FONT>            }<a name="line.60"></a>
<FONT color="green">061</FONT>    <a name="line.61"></a>
<FONT color="green">062</FONT>            // Done<a name="line.62"></a>
<FONT color="green">063</FONT>            return new String(buf);<a name="line.63"></a>
<FONT color="green">064</FONT>        }<a name="line.64"></a>
<FONT color="green">065</FONT>    <a name="line.65"></a>
<FONT color="green">066</FONT>        /**<a name="line.66"></a>
<FONT color="green">067</FONT>         * Decode a {@link String} back into a {@code byte[]} array.<a name="line.67"></a>
<FONT color="green">068</FONT>         * Any extra whitespace in the string is ignored.<a name="line.68"></a>
<FONT color="green">069</FONT>         *<a name="line.69"></a>
<FONT color="green">070</FONT>         * @param text string previously encoded by {@link #encode}, or {@code null}<a name="line.70"></a>
<FONT color="green">071</FONT>         * @return original {@code byte[]} array (or {@code null} if {@code text} was {@code null})<a name="line.71"></a>
<FONT color="green">072</FONT>         * @throws IllegalArgumentException if any invalid non-whitespace characters are seen, or the number of hex digits is odd<a name="line.72"></a>
<FONT color="green">073</FONT>         */<a name="line.73"></a>
<FONT color="green">074</FONT>        public static byte[] decode(String text) {<a name="line.74"></a>
<FONT color="green">075</FONT>    <a name="line.75"></a>
<FONT color="green">076</FONT>            // Check for null<a name="line.76"></a>
<FONT color="green">077</FONT>            if (text == null)<a name="line.77"></a>
<FONT color="green">078</FONT>                return null;<a name="line.78"></a>
<FONT color="green">079</FONT>    <a name="line.79"></a>
<FONT color="green">080</FONT>            // Allocate array<a name="line.80"></a>
<FONT color="green">081</FONT>            byte[] array = new byte[text.length() / 2];<a name="line.81"></a>
<FONT color="green">082</FONT>    <a name="line.82"></a>
<FONT color="green">083</FONT>            // Parse bytes<a name="line.83"></a>
<FONT color="green">084</FONT>            int len = 0;<a name="line.84"></a>
<FONT color="green">085</FONT>            boolean flipflop = false;<a name="line.85"></a>
<FONT color="green">086</FONT>            int prevNibble = 0;<a name="line.86"></a>
<FONT color="green">087</FONT>            final int limit = text.length();<a name="line.87"></a>
<FONT color="green">088</FONT>            for (int pos = 0; pos &lt; limit; pos++) {<a name="line.88"></a>
<FONT color="green">089</FONT>                char ch = text.charAt(pos);<a name="line.89"></a>
<FONT color="green">090</FONT>                if (Character.isWhitespace(ch))<a name="line.90"></a>
<FONT color="green">091</FONT>                    continue;<a name="line.91"></a>
<FONT color="green">092</FONT>                int nibble = Character.digit(ch, 16);<a name="line.92"></a>
<FONT color="green">093</FONT>                if (nibble == -1)<a name="line.93"></a>
<FONT color="green">094</FONT>                    throw new IllegalArgumentException("invalid character '" + ch + "' in byte array");<a name="line.94"></a>
<FONT color="green">095</FONT>                if (flipflop)<a name="line.95"></a>
<FONT color="green">096</FONT>                    array[len++] = (byte)((prevNibble &lt;&lt; 4) | nibble);<a name="line.96"></a>
<FONT color="green">097</FONT>                else<a name="line.97"></a>
<FONT color="green">098</FONT>                    prevNibble = nibble;<a name="line.98"></a>
<FONT color="green">099</FONT>    <a name="line.99"></a>
<FONT color="green">100</FONT>                // bitwise inversion of boolean<a name="line.100"></a>
<FONT color="green">101</FONT>                flipflop ^= true;<a name="line.101"></a>
<FONT color="green">102</FONT>            }<a name="line.102"></a>
<FONT color="green">103</FONT>            if (flipflop)<a name="line.103"></a>
<FONT color="green">104</FONT>                throw new IllegalArgumentException("byte array has an odd number of digits");<a name="line.104"></a>
<FONT color="green">105</FONT>    <a name="line.105"></a>
<FONT color="green">106</FONT>            // Account for any squeezed-out whitespace<a name="line.106"></a>
<FONT color="green">107</FONT>            if (len &lt; array.length) {<a name="line.107"></a>
<FONT color="green">108</FONT>                byte[] temp = new byte[len];<a name="line.108"></a>
<FONT color="green">109</FONT>                System.arraycopy(array, 0, temp, 0, len);<a name="line.109"></a>
<FONT color="green">110</FONT>                array = temp;<a name="line.110"></a>
<FONT color="green">111</FONT>            }<a name="line.111"></a>
<FONT color="green">112</FONT>    <a name="line.112"></a>
<FONT color="green">113</FONT>            // Done<a name="line.113"></a>
<FONT color="green">114</FONT>            return array;<a name="line.114"></a>
<FONT color="green">115</FONT>        }<a name="line.115"></a>
<FONT color="green">116</FONT>    }<a name="line.116"></a>
<FONT color="green">117</FONT>    <a name="line.117"></a>




























































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